Add a VirtualBox-based Vagrant config file.

This VagrantFile will, on "vagrant up"...

- Create a simple, minimal Precise Pangolin (12.04) Ubuntu 64 bit VM
- Customize the VM with 2 virtual CPU's and 2048MB of RAM
- Configure SSH for passwordless access (from the command-line)
- Add the required packages from the Ubuntu repo to support zipline
- Add (and compile) ta-lib
- Add the required Pip packages

When Vagrant is done, you can start hacking on zipline with:

vagrant ssh
cd /vagrant
python {some python script that uses zipline}
In the spirit of making this a disposable dev environment install
everything in site-packages.

"nosetests" and "examples/dual_moving_average.py" both succeed
after the configuration finishes.